• 한국지진공학회논문집
• /
• 제11권2호
• /
• pp.81-94
• /
• 2007

지진시 발생하는 지반 액상화 현상은 지진피해예측시 가장 중용하게 평가해야 하는 항목으로 실내에서 액상화 현상을 시뮬레이션하는 경우, 불규칙성의 지진을 제어하기 어려운 이유로 등가반복형태의 정현파 또는 쐐기파를 이용하는 것이 통상적이었다. 그러나, 90년대 이후 컴퓨터의 발달과 함께한 신호처리 및 제어기술의 급속한 발전은 동역학분야에서의 실험연구에 큰 도움을 주었으며 지반진동분야의 경우, 진동대 및 원심모형기와 같은 대형지진모의시험에서 실지진하중을 이용한 연구사례들이 증가되고 있는 실정이다. 국내에서도 실지진하중재하가 가능한 요소시험결과에 대한 연구사례가 발표되는 등 이에 관한 연구가 활발하게 진행되고 있으며 특히, 실지진하중 시험결과로부터 실지진하중하에서의 과잉간극수압의 변화가 정현하중시험에서의 결과와 큰 차이를 보이고 있다는 분석결과가 발표되어 현재까지 지반동역학분야에서 지진하중의 불규칙성을 크게 고려하지 않았던 통상적 가정사항들이 문제점으로 대두되어 관심을 집중시키고 있다. 본 연구에서는 등가의 정현파 및 쐐기파와 증가형태의 쐐기파, 그리고 실지진파 등 다양한 진동하중을 재하할 수 있는 삼축압축시험기를 이용하여 기존의 유효응력개념에서 사용하는 과잉간극수압관련 매개변수인 소성일, 전단소성 변형률 상각궤도, 그리고 액상화 상태전환선의 기울기를 비교분석하였으며 하중변화에 따른 토립자의 변형과 간극수압의 변화를 상세분석하였다. 연구결과, 토립자의 변형, 간극수의 동적흐름, 동적흐름 속도수두의 압력수두로의 전환, 그리고 과잉간극수압의 증가로 표현되는 새로운 개념의 액상화 발생이론을 제안하였으며 그 타당성 검토를 위해 과잉간극수압과 동적흐름의 압력수두(흐름속도의 제곱값)와의 상관관계를 비교하였다.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2004년도 춘계학술대회
• /
• pp.1225-1230
• /
• 2004

In this paper, the pressure drops were investigated according to the sintered porous wick structure in loop heat pipe(LHP) by theoretical analysis. LHP has the wick only in evaporator for the circulation of working fluid, so utilizes porous wick structure which pore diameter is very small for large capillary force. This paper investigates the effects of different parameters on the pressure drops of the LHP such as particle diameter of sintered porous wick, wick porosity, vapor line diameter, thickness of wick and heating capacity. Working fluid is water and the material of sintered porous wick is copper. According to the these different parameters, capillary pressure, pressure drop in wick were analized by theoretical design method of LHP.

• 한국안전학회지
• /
• 제28권5호
• /
• pp.35-40
• /
• 2013

Recently reclamation land is largely developed to utilize the land according to economic growth. The soil of landfill is soft, low shear strength, which makes it difficult to use the equipment. A large movement is occurred on the utility tunnel under construction. The inclined land with high water level and underground facilities are widely distributed and the excess pore water pressure may occur under construction similarly to this study. Some different conditions are made to design result, such as 4m of soil piling near the construction area, heavy rainfall during 2nd excavation that may cause flow liquefaction. To analyze the cause of transverse lateral movement, Three dimensional analysis are performed to four load cases, which is original design condition, flow liquefaction by heavy rainfall, unsymmetric lateral soil pressure, and both of them simultaneously. Ten steps of full construction stage, 1st excavation for utility tunnel, construction of utility tunnel, 1st refill, piling soil from 1m to 4 m, 2nd excavation for drainage culvert, liquefaction around the utility tunnel, construction of drainage culvert and 2nd refill, are take into account to investigate the cause of movement.

• 상하수도학회지
• /
• 제10권3호
• /
• pp.92-99
• /
• 1996

The effects of membrane fouling on the water permeability were examined using the hollow fiber microfiltration (HMF)membrane. A membrane module with a pore size of 0.1 micron was submerged in the permeation tank and water bath. The applied pressure was 12.4 kPa for direct solid-liquid separation of activated sludge. As the concentration of MLSS(880~2180mg/l) of the feed solution increased, the decreasing rates of the water flux increased and the membrane was clogged more rapidly. The water flux through the membrane did not increase effectively even with the increase in the applied pressure(40.0~93.3kPa). When the membrane was cleaned with water, the recovery rate of water flux were larger for lower applied pressure. The results indicated that the process of direct solid-liquid separation using HMF membrane was effective at lower pressure.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2010년도 추계 학술발표회 3차
• /
• pp.135-139
• /
• 2010

A construction technique to install the soil-bentonite (SB) cut-off wall for in-situ geoenvironmental containment by employing the trench cutting and re-mixing deep wall method is first presented in this paper. The laboratory test results on the hydraulic barrier performance of SB in relation to the chemical compatibility are then discussed. Hydraulic conductivity tests using flexible-wall permeameters as well as swell tests were conducted for SB specimens exposed to various types and concentrations of chemicals (calcium chloride, heavy fuel oil, ethanol, and/or seawater) in the permeant and/or in the pore water of original soil. For the SB specimens in which the pore water of original soil did not contain such chemicals and thus the sufficient bentonite hydration occurred, k values were not significantly increased even when permeated with the relatively aggressive chemical solutions such as 1.0 mol/L $CaCl_2$ or 50%-concentration ethanol solution. In contrast, the SB specimens containing $CaCl_2$ in the pore water had the higher k values. The excellent linear correlation between log k and swelling pressure implies that the swelling pressure can be a good indicator for the hydraulic barrier performance of the SB.

• Geomechanics and Engineering
• /
• 제8권3호
• /
• pp.461-476
• /
• 2015

Rankine's theory of earth pressure cannot be directly employed to c-${\phi}$ soils backfill with a sloping ground subjected to complex loadings. In this paper, an analytical solution for active earth pressures on retaining structures of cohesive backfill with an inclined surface subjected to surcharge, pore water pressure and seismic loadings, are derived on the basis of the lower-bound theorem of limit analysis combined with Rankine's earth pressure theory and the Mohr-Coulomb yield criterion. The generalized active earth pressure coefficients (dimensionless total active thrusts) are presented for use in comprehensive design charts which eliminate the need for tedious and cumbersome graphical diagram process. Charts are developed for rigid earth retaining structures under complex environmental loadings such as the surcharge, pore water pressure and seismic inertia force. An example is presented to illustrate the practical application for the proposed coefficient charts.

• 펄프종이기술
• /
• 제37권4호통권112호
• /
• pp.32-37
• /
• 2005

To Increase the productivity of a paper machine, the maximization of the machine speed is a kind of simple way As the machine speed increases, more intense wet pressing is required to persist the outlet consistency of press part and reduce the water removal of dryer part. With more intense pressing, there are concerns that the quality of paper will be affected. This study was carried out to evaluate the influence of wet-pressing on internal structure of paper, The nip pressure at the first and third nip in triple nip press was controlled. Paper structures, strength properties and pore properties were evaluated. As a result, first nip pressure more strongly influenced the paper structural properties than third nip pressure in triple nip pressing condition. Because of the high water content and low wet-web strength of paper web in first nip, increasing the first nip pressure induced the incipient crushing of wet-web and then caused a potential of web break during the following coating or printing processes.

• 한국지반환경공학회 논문집
• /
• 제17권2호
• /
• pp.31-39
• /
• 2016

일반적으로 고함수비를 가진 연약지반의 경우 압밀 촉진을 원활히 하기 위하여 연직배수재를 주로 사용하고 있다. 부산 점토는 대심도 연약지반 아래에 존재하는 모래 및 자갈 대수층에 피압이 관측되었다. 그러나 연직배수재가 설치된 연약지반에 피압이 미치는 영향에 대한 조사나 연구는 미미한 실정이다. 따라서 본 논문에서는 연직배수재가 설치된 부산 낙동강 하구 연약지반에 피압의 작용 유 무에 따른 압밀 거동을 조사하기 위해 일차원 대형 컬럼 장치를 제작하여 점토지반의 압밀 거동 실험을 수행하였다. 실험 결과 최종 침하량은 피압이 작용하는 지반이 피압이 작용하지 않는 지반보다 더 크게 나타났다. 이는 피압의 상향침투로 인해 점토층의 유효응력이 감소하여 나타난 결과로 판단된다. 또한 피압이 작용하는 지반의 경우 과잉간극수압이 완전 소산되지 않고 잔류하는 것으로 나타났으며, 비배수 전단강도는 피압이 작용하지 않는 지반에 비해 상대적으로 낮은 값을 나타내었다.

• 한국농공학회지
• /
• 제35권3호
• /
• pp.47-62
• /
• 1993

The laboratorv model test was carried out to investigate the behavior of pore water pressure, the critical amount of rainfall for slope failure, the pattern of failure, and the variation of seepage line at the slope with the uniform material of embankment by changing the slope angles and rainfall intensities. The results were was summarised as follows : 1.At the beginning stage of rainfall, the negative pore pressure appeared at the surface of slope and the positive pore pressure at the deep parts. But, the negative one turned into the positive one as the rainfall continued and this rapidly increased about 50 to 100 minutes before the slope failure. 2.The heavier the rainfall intensity, the shorter the time, and the milder the slope, the longer the time took to reach the failure of slope. 3.As the angle of the slope became milder, the critical amount of rainfall for slope failure became greater. 4.Maximum pore water pressure was 10 to 40g/cm$^2$ at the toe of slope and 50 to 90g/cm$^2$at the deep parts. 5.In the respect of the pattern of slope failure, surface failure of slope occurred locally at the toe of slope at the A-soil and failure of slope by surface flow occurred gradually at the top part of slope at the B-soil. 6.As the rainfall continued and the saturation zone in the embankment was formed, the seepage line went rapidly up and also the time to reach the total collapse of slope took longer at the B-soil. 7.As the position of the seepage line went up and the strength parameter accordingly down, the safety factor was 2.108 at the A-soil and 2.150 at the B-soil when the slope occured toe failure. Minimum safety factor was rapidly down to 0.831 at the A-soil and to 0.936 at the B-soil when the slope collapsed totally at the top part of slope.

• 한국지반공학회논문집
• /
• 제19권4호
• /
• pp.15-21
• /
• 2003

본 연구는 풍화 화강토의 일정 간극비에서 초기함수비의 변화에 따른 거동 특성을 통상의 삼축압축시험기를 이용한 비배수시험을 실시하여 비배수전단시 불포화 풍화 화강토의 간극압, 체적변형 및 응력-변형률 거동특성을 밝히고자한다. 연구에 사용된 시료는 조립질의 풍화 화강토이고 직경 50mm 높이 100mm로 복층다짐하여 삼축 시험용 공시체를 제작하였다. 준비된 공시체를 구속압력과 흡인력($u_a-u_w$)을 각각 달리한 비배수 3축압축시험을 실시하였다. 그 결과 초기 함수비의 변화에 따라 내부마찰각($\phi'$)의 변화는 다소 있지만 흡인력의 변화에 따른 내부마찰각의 변화는 거의없고 유효점착력만이 증가하는 경향을 보이고 있다.